code: def test_HandleUnknown_HaveOnlyKnown_ExpectSecondColumn(self):
      train = ["A", "B"]
  
      encoder = encoders.OneHotEncoder(
          handle_unknown="indicator", handle_missing="value"
      )
      result = encoder.fit_transform(train)
  
      expected = [[1, 0, 0], [0, 1, 0]]
      self.assertEqual(result.to_numpy().tolist(), expected)
  
imports: import pandas
  from unittest import TestCase
  import numpy
  import tests.helpers
  import category_encoders
label_desc: Use image node_id 18 for calling the TestOneHotEncoderTestCase obj's underlying member method code with example usage: obj.test_HandleUnknown_HaveOnlyKnown_ExpectSecondColumn() without return types